THE PRESENT INVENTION relates to an ejection seat rocket motor and, more particularly, relates to a rocket motor intended for use with an ejection seat in an aircraft.
Ejection seats are commonly used in military- aircraft where the risk of aircraft failure or combat damage is high. Ejection seats allow the air crew to escape from stricken aircraft and typically provide a safe, reliable means of escape.
Ejection seats are conventionally provided with an elongate rocket motor fitted to the seat below the sitting platform and positioned in such a way that the thrust of the rocket motor acts close to the centre of gravity of the seat/occupant combination. Such rocket motors are positioned transversely across the seat and have exhaust nozzles at either end to allow for the passage of exhaust gases therethrough. The thrust from the rocket motor serves to fire the ejection seat away from the aircraft. However, it is usual only to fire the main rocket motor of an ejection seat once the ejection seat is clear of the aircraft. Initial propulsion of the ejection seat out of the aircraft cockpit is effected by one or more pyrotechnic charges which serve to eject the seat from the cockpit along a system of rails. Only once the seat is clear of the cockpit is the rocket motor fired to ensure that a safe distance is put between the seat and the aircraft tail and then to allow full and safe deployment of the ejection seat parachute.
It is advantageous to be able to control the trajectory of an ejection seat from the aircraft cockpit rather than simply to rely upon a substantially vertical trajectory. One particular instance in which such control of the ejection seat trajectory is advantageous is in the situation of an aircraft cockpit housing two air crew, for example, a pilot and co-pilot. In this situation it is advantageous to eject the pilot and co-pilot along diverging trajectories so as to avoid or at least minimise the risk of the pilot and co-pilot colliding with one another upon ejection from the aircraft. There are other situations in which a non-vertical ejection trajectory is advantageous, as will be explained in more detail hereinafter.
One known way in which divergence of pilot and co-pilot ejection trajectories is effected is to provide each ejection seat with an additional rocket motor to provide lateral thrust. For example, the pilot""s ejection seat may be provided with a thrust nozzle pointing towards the port side of the aircraft whilst the co-pilot""s ejection seat may be provided with a thrust nozzle pointing towards the starboard side of the aircraft. Upon ejection, these additional rocket motors provide lateral thrust in opposite directions to direct the pilot""s and co-pilot""s seats along diverging trajectories away from one another. However, this type of arrangement suffers from several disadvantages. For example, the addition of extra lateral thrust rocket motors adds to the aircraft""s total mass, increases the cost of the ejection seat and results in a bulky ejection seat causing problems of installation within the aircraft cockpit.
Another known way to provide control over the trajectory of an ejection seat is to provide the main rocket motor with a thrust vector control arrangement. Such thrust vector control arrangements are well-known in the art but are disadvantageous for use with ejection seats because they are complicated and add both weight and cost to the installation.
It is an object of the present invention to provide an improved ejection seat rocket motor.
According to one aspect of the present invention, there is provided an ejection seat rocket motor comprising a combustion chamber, a plurality of spaced apart exhaust outlets in fluid communication with the combustion chamber to allow the passage of exhaust gases upon ignition of a propellant within the combustion chamber, each exhaust outlet being arranged to direct the exhaust gases along a respective fixed line of thrust, the arrangement being such that the resultant thrust generated acts along a line non-parallel with at least one of the fixed lines of thrust so as to direct the rocket motor along a curved trajectory.
Preferably, the thrust generated by at least one of the exhaust outlets differs in magnitude from the thrust generated by the or each other exhaust outlets.
Advantageously, the exhaust outlets are arranged such that their respective fixed lines of thrust are all substantially parallel with one another.
Conveniently, the ejection seat rocket motor further comprises selection means operable to select from said plurality of exhaust outlets, one or more exhaust outlets through which to allow the passage of exhaust gas upon ignition of the propellant within the combustion chamber.
According to another aspect of the present invention, there is provided an ejection seat rocket motor comprising a combustion chamber, a plurality of exhaust outlets in fluid communication with the combustion chamber, and selection means operable to select from said plurality of exhaust outlets one or more exhaust outlets through which to allow the passage of exhaust gas upon ignition of a propellant within the combustion chamber.
Preferably, said selection means comprises a valve means associated with at least one of the plurality of exhaust outlets, the valve means being moveable from a first position in which substantially no exhaust gas is allowed to pass through the respective exhaust outlet, to a second position in which substantially unrestricted flow of exhaust gas is allowed through the respective exhaust outlet.
Advantageously, said selection means comprises a valve means associated with at least one of the plurality of exhaust outlets, the valve means being moveable from a first position in which substantially unrestricted flow of exhaust gas is allowed through the respective exhaust outlet, to a second position in which substantially no exhaust gas is allowed to pass through the respective exhaust outlet.
Conveniently, the ejection seat rocket motor further includes valve indicator means arranged to provide a visual indication from outside the rocket motor and whether the or each valve means is in its respective first or second position.
Advantageously, said selection means comprises a fuse actuable to allow movement of one or more of said valve means from their respective first positions to their respective second positions.
Conveniently, said selection means comprises a separate said fuse associated with each said valve means.
Preferably, the or each fuse comprises an exclusive charge.
Advantageously, the or each fuse is arranged to move a locking element into or out of locking engagement with the or each valve means upon actuation of the fuse so as to prevent or allow respectively movement of the or each valve means from its first position to its second position.
Conveniently, the ejection seat rocket motor further includes locking element indicator means arranged to provide a visual indication from outside the rocket motor of whether the or each locking element is in or out of locking engagement with the or each valve means.
Preferably, the ejection seat rocket motor comprises at least one primary exhaust outlet and at least one secondary exhaust outlet, the magnitude of thrust produced by the or each primary exhaust outlet upon ignition of a propellant within the combustion chamber being greater than the magnitude of thrust produced by the or each second exhaust outlet.
Advantageously, the or each primary exhaust outlet is arranged so as always to allow the passage of exhaust gas upon ignition of a propellant within the combustion chamber.
Conveniently, the selection means is arranged to select whether or not to allow the passage of exhaust gas to any of the or each secondary exhaust outlets.
Preferably, the ejection seat rocket motor is provided with an ignition fuse to ignite a propellant within the combustion chamber.
Advantageously, each exhaust outlet is provided with an nozzle.
Conveniently, the ejection seat rocket motor is provided with a combustible propellant within a combustion chamber.
Preferably, the propellant is a composite propellant comprising a fuel and an oxidant.
Advantageously, the propellant is non-platonised.
There is also provided an ejection seat provided with a rocket motor in accordance with the present invention.